Mohamed Ghannam discovered that the DCCP implementation did not
correctly manage resources when a socket is disconnected and
reconnected, potentially leading to a use-after-free. A local
user could use this for denial of service (crash or data
corruption) or possibly for privilege escalation. On systems that
do not already have the dccp module loaded, this can be mitigated
by disabling it:
echo>> /etc/modprobe.d/disable-dccp.conf install dccp false

Andrey Konovalov reported that the dvb-usb-lmedm04 media driver
did not correctly handle some error conditions during
initialisation. A physically present user with a specially
designed USB device can use this to cause a denial of service
(crash).

Andrey Konovalov reported that the hdpvr media driver did not
correctly handle some error conditions during initialisation. A
physically present user with a specially designed USB device can
use this to cause a denial of service (crash).

Kevin Cernekee discovered that the netfilter subsystem allowed
users with the CAP_NET_ADMIN capability in any user namespace, not
just the root namespace, to enable and disable connection tracking
helpers. This could lead to denial of service, violation of
network security policy, or have other impact.

Kevin Cernekee discovered that the netlink subsystem allowed
users with the CAP_NET_ADMIN capability in any user namespace
to monitor netlink traffic in all net namespaces, not just
those owned by that user namespace. This could lead to
exposure of sensitive information.

Andrey Konovalov reported that that USB core did not correctly
handle some error conditions during initialisation. A physically
present user with a specially designed USB device can use this to
cause a denial of service (crash or memory corruption), or
possibly for privilege escalation.

Dmitry Vyukov reported that the KVM implementation for x86 would
over-read data from memory when emulating an MMIO write if the
kvm_mmio tracepoint was enabled. A guest virtual machine might be
able to use this to cause a denial of service (crash).

It was discovered that some implementations of the Salsa20 block
cipher did not correctly handle zero-length input. A local user
could use this to cause a denial of service (crash) or possibly
have other security impact.

It was discovered that the HMAC implementation could be used with
an underlying hash algorithm that requires a key, which was not
intended. A local user could use this to cause a denial of
service (crash or memory corruption), or possibly for privilege
escalation.

Eric Biggers discovered that the KEYS subsystem lacked a check for
write permission when adding keys to a process's default keyring.
A local user could use this to cause a denial of service or to
obtain sensitive information.

Alexei Starovoitov discovered that the Extended BPF verifier
ignored unreachable code, even though it would still be processed
by JIT compilers. This could possibly be used by local users for
denial of service. It also increases the severity of bugs in
determining unreachable code.

Jann Horn discovered that the Extended BPF verifier could fail to
detect pointer leaks from conditional code. A local user could
use this to obtain sensitive information in order to exploit
other vulnerabilities.

Andrew Honig reported that the KVM implementation for Intel
processors allowed direct access to host I/O port 0x80, which
is not generally safe. On some systems this allows a guest
VM to cause a denial of service (crash) of the host.

Ben Seri reported that the Bluetooth subsystem did not correctly
handle short EFS information elements in L2CAP messages. An
attacker able to communicate over Bluetooth could use this to
obtain sensitive information from the kernel.

The various problems in the Extended BPF verifier can be mitigated by
disabling use of Extended BPF by unprivileged users:
sysctl kernel.unprivileged_bpf_disabled=1

Debian disables unprivileged user namespaces by default, but if they
are enabled (via the kernel.unprivileged_userns_clone sysctl) then
CVE-2017-17448 can be exploited by any local user.

For the stable distribution (stretch), these problems have been fixed in
version 4.9.65-3+deb9u1.